U.S. patent application number 10/512850 was filed with the patent office on 2005-07-07 for apparatus and an associated method for facilitating communications in a radio communication system that provides for data communications at multiple data rates.
Invention is credited to Pi, Zhouyue, Rong, Zhigang.
Application Number | 20050147063 10/512850 |
Document ID | / |
Family ID | 29739918 |
Filed Date | 2005-07-07 |
United States Patent
Application |
20050147063 |
Kind Code |
A1 |
Pi, Zhouyue ; et
al. |
July 7, 2005 |
Apparatus and an associated method for facilitating communications
in a radio communication system that provides for data
communications at multiple data rates
Abstract
Apparatus, and an associated method, for facilitating operation
of a radio communication system that provides for multi rate data
communications, such as a CDMA 2000 system that provides for
1xEV-DV communication services. A supplemental pilot, or control,
signal generator embodied at a mobile station generates a
supplemental pilot, or control, signal that is sent on a newly
defined supplemental pilot, or control, channel. As the data rates
of data communicated upon a reverse supplemental channel changes,
corresponding changes are made to the power level of the reverse
supplemental pilot, or control, signal.
Inventors: |
Pi, Zhouyue; (San Diego,
CA) ; Rong, Zhigang; (San Diego, CA) |
Correspondence
Address: |
SCHEEF & STONE, L.L.P.
5956 SHERRY LANE
SUITE 1400
DALLAS
TX
75225
US
|
Family ID: |
29739918 |
Appl. No.: |
10/512850 |
Filed: |
October 28, 2004 |
PCT Filed: |
June 5, 2003 |
PCT NO: |
PCT/US03/17625 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60386819 |
Jun 7, 2002 |
|
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60386906 |
Jun 7, 2002 |
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Current U.S.
Class: |
370/335 ;
370/342 |
Current CPC
Class: |
H04W 52/0229 20130101;
H04W 28/22 20130101; H04W 52/0216 20130101; H04W 52/267 20130101;
Y02D 30/70 20200801; H04W 52/26 20130101; H04W 52/16 20130101; H04W
52/12 20130101; H04W 36/16 20130101 |
Class at
Publication: |
370/335 ;
370/342 |
International
Class: |
H04B 007/216 |
Claims
We claimed:
1. In a radio communication system in which data is communicated by
a first communication station on at least a first data channel at
least at a first selected data rate and in which a first control
signal is communicated on a first control channel, the first
control signal targeted at a first trigger level during at least a
first selected time period, an improvement of apparatus for
facilitating communication of the data on the at least the first
data channel, said apparatus comprising: a second control signal
generator for selectably generating a second control signal for
communication upon a second control channel, the second control
signal targeted at a second target level, the second target level
selected responsive to the at least the first selected data rate at
which the data is communicated on the at least the first selected
data rate at which the data is communicated on the at least the
first data channel.
2. The apparatus of claim 1 wherein the facilitating of the
communication of the data comprises facilitating coherent
demodulation of the data communicated upon the at least the first
data channel, and wherein the second target level of the second
control signal is directly proportional, at least in a stepwise
manner, to the first selected data rate at which the data is
communicated on the at least the first data channel.
3. The apparatus of claim 1 wherein the first control signal
comprises a first pilot signal, communicated upon a first pilot
channel, and wherein said second control signal generator comprises
a second pilot signal generator for generating a second pilot
signal, the second pilot signal of the second target level.
4. The apparatus of claim 3 wherein the radio communication system
comprises a cellular radio communication system having a network
part, wherein the first communication station comprises a mobile
station operable in the cellular radio communication system, and
said second pilot signal generator is embodied at the mobile
station.
5. The apparatus of claim 4 wherein the cellular radio
communication system comprises a multiple data rate system in which
the data communicated by the mobile station of the at least the
first selected data rate is selectably of the first data rate and
at least a second data rate and wherein the second target level is
of a first value when the data is of the first data rate and is of
a second value when the data is of the second data rate.
6. The apparatus of claim 1 wherein the at least the first data
upon which data is communicated comprises a first data channel at
the first selected data rate and at least a a second data channel
at least at a second selected data rate and wherein the second
target level at which the second control signal is targeted is
responsive to the at least the second selected data rate at which
the data is communicated on the at least the second data
channel.
7. The apparatus of claim 6 wherein the radio communication system
defines a reverse fundamental channel (R-FCH) and at least a first
reverse supplemental channel (R-SCH), wherein the first data
channel comprises the reverse fundamental channel, wherein the
second data channel comprises the first reverse supplemental
channel.
8. The apparatus of claim 1 wherein the first trigger level
comprises a first signal-to-noise ratio and wherein the second
trigger level comprises a second signal-to-noise ratio, the second
signal-to-noise ratio selected responsive to the at least the first
selected data rate at which the data is communicated on the at
least the first data channel.
9. The apparatus of claim 1 wherein the at least the first data
channel comprises the first data channel and at least a second data
channel and wherein the first target level at which the first
control signal is targeted during the at least the first selected
time period comprises a nominal value required to communicate the
data upon the first data channel, and wherein the second target
level at which the second control signal is targeted is targeted
during the first selected time period.
10. The apparatus of claim 9 wherein the data is communicated upon
the second data channel at a second selected rate and wherein the
second target level is selected responsive to the second selected
rate at which the data is communicated upon the second data
channel.
11. The apparatus of claim 10 wherein the second target level is
selected responsive to the second selected rate at which the data
is communicated upon the second data channel during a prior time
period, the prior time period prior to the first selected time
period.
12. The apparatus of claim 1 wherein the second control signal
generated by said second control signal generator is
unmodulated.
13. The apparatus of claim 1 wherein the second control signal
generated by said second control signal generator is modulated by a
known sequence.
14. In a method of communicating in a radio communication system in
which data is communicated by a first communication station on at
least a first data channel at least at a first selected data rate
and in which a first control signal is communicated on a first
control channel, the first control signal targeted at a first
target level during at least a first selected time period, an
improvement of a method for facilitating communication of the data
on the at least the first data channel, said method comprising:
selecting a second target level at which to send a second control
signal on a second control channel, the second target level
selected responsive to the at least the first selected data rate at
which the data is communicated on the at least the first data
channel; and selectably sending the second control signal of
characteristics selected during said operation of selecting upon
the second control channel.
15. The method of claim 14 wherein the first data channel comprises
a first pilot channel and the first control signal comprises a
first pilot signal, and wherein the second control signal, the
second target level of which is selected during said operation of
selecting comprises a second pilot signal.
16. The method of claim 15 wherein the at least the first data
channel comprises the first data channel and at least a second data
channel wherein the data communicated upon the second data channel
is at least selectably of the first selected data rate and a second
selected data rate and wherein the second target level selected
during said operation of selecting is of a value proportional, at
least in a stepwise manner, with at which of the first selected
data rate and the second selected data rate at which the data is
communicated on the second data channel.
17. The method of claim 14 wherein the first control signal and the
second control signal are, at least during a selected interval,
concurrently sent, and wherein the first and second target levels,
respectively, are of levels that permit coherent demodulation of
the data communicated on the at least the first data channel.
18. The method of claim 14 wherein the at least the first data
channel comprises the first data channel and at least a second data
channel, and wherein the second target level selected during said
operation of selecting is selected to permit coherent demodulation
of the data communicated on the second data channel.
19. The method of claim 18 wherein the second target level selected
during said operation of selecting is selected responsive to data
communicated upon the second data channel during a prior time
period, the prior time period prior to the first selected time
period.
20. The method of claim 14 wherein the radio communication system
comprises a multiple data rate system in which the data
communicated by the first communication station of the at least the
first selected data rate is selectably of the first data rate and
at least a second data rate and wherein the second target level
selected during said operation of selecting is of a first value
when the data is of the first data rate and is of a second value
when the data is of the second data rate.
21. In a cellular communication system generally operable pursuant
to a cdma 2000 operating specification and that provides for
variable data rate communications, the communication system
defining a fundamental reverse pilot channel upon which a mobile
station communicates a reverse fundamental pilot signal to
facilitate demodulation of the first data communicated upon a
reverse fundamental data channel, an improvement of apparatus for
the mobile station for facilitating demodulation of second data
communicated upon a reverse supplemental data channel, said
apparatus comprising: a reverse supplemental pilot signal generator
embodied at the mobile station, said reverse supplemental pilot
signal generator for generating a reverse supplemental pilot signal
upon a reverse supplemental pilot channel, the reverse supplemental
pilot signal targeted at a supplemental channel target level, the
supplemental channel target level selected responsive to a data
rate of the second data.
22. A method for facilitating detection of data received at a
receiving station from a sending station, the method comprising the
steps of: determining a rate at which data is to be transmitted on
a supplemental channel of a radio communication channel;
determining a quantity of pilot channel power required by a
receiver of said data to estimate values of bits of said data
transmitted at said data rate on said supplemental channel;
appending a supplemental pilot channel to a fundamental pilot
channel of said reverse link, said supplemental pilot channel
comprising said quantity of power required by said receiver of the
data to estimate values of bits of the data; and repeating the
foregoing steps when the rate at which data is to be transmitted on
said reverse link changes.
23. In a radio communication system in which data is communicated
by a first communication station on at least a first data channel
at least at a first selected data rate, an improvement of apparatus
for facilitating communication of the data on the at least the
first data channel, said apparatus comprising: a control signal
generator for selectably generating a control signal for
communication upon a control channel, the control signal targeted
at a target level at least during a selected time period responsive
to the at least the first selected data rate at which the data is
communicated on the at least the first data channel.
Description
[0001] The present invention relates generally to a manner by which
to facilitate communications in a radio communication system that
provides for data communications at multiple data rates, such as a
CDMA 2000 cellular communication system that provides for 1xEV-DV
data communication services. More particularly, the present
invention relates to apparatus, and an associated method, that
provides a pilot, or other control, signal, of levels related to
the data rates at which the data is communicated. When the data
rate at which data is communicated is changed, the levels at which
the pilot, or other control, signal is generated correspondingly
changes.
[0002] Because the pilot, or other control, signal is of a level
matched with the data rate at which data is communicated, the need
otherwise to select a highest power level corresponding to a
highest data rate, best to ensure successful communication of the
data, is obviated. By permitting operation at reduced power levels,
lessened amounts of power are consumed during communications, and
improved system performance and capacity are permitted.
BACKGROUND OF THE INVENTION
[0003] Communication systems are endemic in modern society.
Communication of data pursuant to many varied types of
communication services is regularly needed. A communication system
is used by which to effectuate the communication of the data. Due
to advancements in communication technologies, new types of
communication systems are being developed.
[0004] A communication system includes at least a first
communication station and a second communication station
interconnected by way of a communication channel. Data is
communicated by the first communication station, referred to as a
sending station, to the second communication station, referred to
as a receiving station, by way of the communication channel. Data
that is to be communicated by the sending station is converted, if
needed, into a form to permit the data to be communicated upon the
communication channel. And, the receiving station detects the data
communicated upon the communication channel and recovers the
informational content thereof.
[0005] A radio communication system is a type of communication
system. In a radio communication system, a radio channel, defined
upon a radio air interface, forms the communication channel
interconnecting the sending and receiving stations. Conventional
wireline communication systems, in contrast, require the use of
fixed, wireline connections extending between the communications
stations upon which to define the communication channel.
[0006] A radio communication system provides various advantages in
contrast to a wireline counterpart. Initial installation and
deployment costs associated with a radio communication system are
generally less than the costs required to install and deploy a
corresponding wireline communication system. And, a radio
communication system can be implemented as a mobile communication
system in which one or more of the communication stations operable
therein is permitted mobility.
[0007] A cellular communication system is an exemplary type of
mobile radio communication system. Cellular communication systems
have been installed throughout significant portion of the populated
areas of the world and have achieved wide levels of usage. A
cellular radio communication system is a multi-user communication
system in which radio communications are provided with a plurality
of mobile stations. Telephonic communication of voice and data is
effectuable by way of the mobile stations. Mobile stations are
sometimes of sizes to permit their convenient carriage by users of
the mobile stations.
[0008] A cellular radio communication system includes network
infrastructure, that is installed throughout the geographical area
that is encompassed by the communication system. Mobile stations
operable in the cellular communication system communicate, by way
of radio channels, with base stations that form parts of the
network infrastructure of the communication system.
[0009] Base stations are fixed-site radio transceiver that
transceive data with the mobile stations. The base stations are
installed at spaced-apart locations throughout the geographical
area encompassed by the communication system. Each of the base
stations defines a cell, formed of a portion of the geographical
area. A cellular communication system is so-called because of the
cells that together define the coverage area of the communication
system.
[0010] When a mobile station is positioned within a cell defined by
a base station, communications are generally effectuable with the
base station that defines the cell. Due to the inherit mobility of
a mobile station, the mobile station might travel between cells
defined by different ones of the base stations. Continued
communications with the mobile station is provided through
communication hand off procedures between successive ones of the
base stations defining the successive ones of the cells through
which the mobile station passes. Through appropriate positioning of
the base stations, the mobile station, wherever positioned within
the area encompassed by the communication system, shall be within
communication proximity of at least one base station.
[0011] Only relatively low-powered signals need to be generated to
effectuate communications between a mobile station and a base
station when the base stations are suitably positioned at selected
spaced-apart locations. Hand-offs of communications between the
successive base stations permit continued communications without
necessitating increases in the power levels at which the
communication signals are transmitted. And, because the signals
that are generated are all generally of low powered levels, the
same radio channels are able to be reused at different locations of
the cellular communication system. The frequency spectrum allocated
to a cellular communication system is thereby efficiently
utilized.
[0012] A cellular communication system is constructed, generally,
to be operable pursuant to an operating specification of a
particular communication standard. Successive generations of
communication standards have been developed, and operating
specifications defining their operational parameters have been
promulgated. First-generation and second-generation cellular
communication systems have been deployed and have achieved
significant levels of usage. Third-generation and
successor-generation systems are undergoing development,
standardization, and, at least with respect to the third-generation
systems, partial deployment.
[0013] An exemplary third-generation cellular communication system
is a system that operates pursuant to the operating protocol set
forth in a CDMA 2000 operating specification. A CDMA 2000 cellular
communication system, constructed in conformity with the CDMA 2000
operating specification, provides for packet-based data
communication services.
[0014] Various technology proposals by which to effectuate
communication of packet data at high data rates in a CDMA 2000
communication system have been proposed. By transmitting data at
high data rates, increased amounts of data are able to be
communicated in a given time period.
[0015] The 1xEV-DV data communication service is one such proposal.
And, the 1xEV-DO data communication service is another such
proposal. These data communication services provide for the
communication of data at any of several selected data rates. And,
systems providing for such communication services are sometimes
referred to as being multi rate communication systems. Other
communication systems that permit data to be communicated at any of
two or more different data rates are also sometimes referred to as
being multi rate, or multiple, data rate systems.
[0016] In the CDMA 2000 system that provides for multiple data rate
communication services, data that is to be communicated is
communicated at selected data rates on reverse links. That is to
say, data that is communicated by a mobile station to a network
portion of the communication system is communicated, upon a reverse
link channel at a selected data rate. A Pilot signal is also
communicated by the mobile station to the network infrastructure
along with the communication of the data. The pilot signal is
communicated upon a reverse pilot channel, and the data is
communicated upon a data channel. The pilot signal is used at the
network infrastructure to assist in coherent demodulation of the
data communicated upon the data channel.
[0017] In conventional CDMA 2000 systems, i.e., CDMA communication
systems that do not provide for high data rate communications at
multiple data rates that are quickly changeable, the pilot signal
is of a constant, or slowly changing, signal-to-noise ratio (SNR)
level (e.g., received pilot signal to noise ratio). However, when
employed in a system that provides for multiple data rate
communications, such as 1xEV-DV communication services, fast
scheduling and rate control impact the power control operation of
the communication system. Conventionally, the SNR level of the
pilot signal must be set at a high SNR level to ensure successful
communication of the data at a highest data rate of the multiple
data rates. In the event that data is communicated at a data rate
that is lower than the highest data rate, the pilot signal is of a
SNR level that is greater than that which is needed. The pilot
signal, during such times, therefore, is of an excessive power
level. Communication performance in the communication system is
adversely affected. And, when the mobile station is powered by a
battery power supply, the battery power supply is depleted of
stored energy at a rate greater than that which is required.
[0018] If a better manner could be provided by which better to
match the power level of the pilot signal with the data rate at
which the data associated therewith is communicated, improved
system performance would be possible.
[0019] It is in light of this background information related to
radio communication systems capable of communicating data at
multiple data rates that the significant improvements of the
present invention have evolved.
SUMMARY OF THE INVENTION
[0020] The present invention, accordingly, advantageously provides
apparatus, and an associated method, by which to facilitate
communications in a radio communication system that provides for
data communications at multiple data rates.
[0021] Through operation of an embodiment of the present invention,
a pilot, or other control, signal is provided that is of levels
related to the data rates at which the data is communicated. When
the data rate at which data is communicated is changed, the levels
at which the pilot, or other control, signal is generated
correspondingly changes.
[0022] That is to say, through operation of an embodiment of the
present invention, the pilot, or other control, signal is of a
level that is matched with the data rate at which the data is
communicated. The need otherwise to select a highest power level
corresponding to a highest data rate to ensure successful
communication of the data is obviated. Operation is permitted,
thereby, at reduced power levels. And, lessened amounts of power
are consumed during communication operations, and improved system
performance and increased system capacity are permitted.
[0023] When implemented in a CDMA 2000, cellular communication
system that provides for multiple data rates of data
communications, such as the date rates available in an 1xEV-DV
communication service, extra pilot power on the reverse link is
provided. The existing operating specification defines, on the
reverse link, extending from a mobile station to the network
infrastructure of the communication system, both a reverse
fundamental channel and a reverse supplemental channel. The reverse
supplemental channel is provided in significant part, for the
communication of data pursuant to a 1xEV-DV communication
service.
[0024] A reverse pilot channel is also defined. The pilot signal is
sent by the mobile station on the reverse pilot channel along with
data on the reverse fundamental channel.
[0025] Pursuant to operation of an embodiment of the present
invention, a reverse supplemental pilot channel is also defined.
And, the mobile station additionally, selectably, sends a
supplemental pilot signal thereon. The data communicated upon the
reverse fundamental channel is, for instance, of constant, or
varying among a set of predefined low, data rates. The pilot signal
sent on the reverse pilot channel is selected to be of a level,
preferably the smallest possible level, to permit coherent
demodulation of the data communicated upon the reverse fundamental
channel. The pilot signal on the reverse supplemental pilot channel
is of a power level selected responsive to the data rate at which
the data is sent upon the reverse supplemental channel. When the
data rate of the data communicated upon the reverse supplemental
channel is high, the power level of the supplemental pilot signal
sent on the reverse supplemental pilot channel is correspondingly
high. And, when the data rate of the data communicated upon the
supplemental channel is low, the power level at which the reverse
supplemental pilot signal is sent is correspondingly low. By
reducing the power level of the supplemental pilot signal when the
data rate of the associated data is low, the power levels of the
pilot signals are matched with the data rates of the data that is
communicated. And, thereby, transmission of the pilot signals at
power levels exceeding those that are needed coherently to
demodulate the data communicated upon the reverse fundamental and
supplemental channels does not occur. Battery power consumption at
the mobile station is not unnecessarily consumed, and signal energy
on the radio air interface extending between the mobile station and
the network infrastructure is not unnecessarily high.
[0026] In one implementation, the pilot power level of the pilot
signal sent on the reverse pilot channel is always of a level
needed for the operation of the reverse fundamental channel. That
is to say, the T/P ratio of the reverse fundamental channel is
independent of the rate in the reverse supplemental channel. That
extra pilot power needed for operation of the reverse supplemental
channels is provided by the supplemental pilot signal sent upon the
reverse supplemental pilot channel. Fast power control is performed
at the network infrastructure, responsive to either the pilot
signal sent upon the reverse pilot channel alone, or responsive to
the pilot signals communicated upon both of the reverse pilot
channel and the reverse supplemental pilot channel.
[0027] In another implementation, the mobile station always sets
the power level of the pilot signal sent upon the reverse pilot
channel. Thereby, the T/P ratio of the data sent upon the reverse
fundamental channel is set according to the reverse supplemental
channel data rate of a prior frame of data, i.e., data sent during
a preceding time period. As the network infrastructure is aware of
the data rate of the data communicated during a prior time period,
the network infrastructure is also aware of the current T/P ratio
upon the reverse fundamental channel. And, the network
infrastructure adjusts the outer loop power control set point
responsive thereto. If the reverse supplemental channel requires
additional pilot power, in addition to the pilot power provided
upon the reverse pilot channel, then the reverse supplemental pilot
signal sent upon the reverse supplemental channel is used to
provide, and obtain, the additional power that is needed.
[0028] Pursuant to an additional embodiment of the present
invention, a manner is provided by which to facilitate stabling
power control in the event of a data rate change of communication
of data during operation of the communication system. In one
implementation, the adjustment of the pilot reference level is
delayed. In another implementation, conservative power level
setting during rate and power control transition is provided. And,
in another implementation, fast rate indications are provided.
[0029] In these and other aspects, therefore, apparatus, and an
associated method, is provided for a radio communication system.
The radio communication system provides for the communication of
data by a first communication station on at least a first data
channel, at least at a first selected data rate. A first control
signal is communicated upon a first control channel in which the
first control signal is targeted at a first trigger level during at
least a first selected time period. Communication of the data on
the at least the first data channel is facilitated. A second
control signal generator selectably generates a second control
signal for communication upon a second control channel. The second
control signal is targeted at a second target level. The second
target level is selected responsive to the at least the first
selected data rate at which the data is communicated on the at
least the first data channel.
[0030] A more complete appreciation of the present invention and
the scope thereof can be obtained from the accompanying drawings,
which are briefly summarized below, the following detailed
description of the presently-preferred embodiments of the
invention, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 illustrates a functional block diagram of a radio
communication system operable pursuant to an embodiment of the
present invention.
[0032] FIG. 2 illustrates a representation of the relationship
between the data rates of data communicated upon reverse
fundamental and supplemental channels and the power levels of pilot
signals sent on reverse pilot and reverse supplemental pilot
channels during operation of an embodiment of the present
invention.
[0033] FIG. 3 illustrates a representation, similar to that shown
in FIG. 2, also representative of the relationship between data
rates at which data is communicated on reverse link channels and
power levels of pilot signals generated on reverse pilot and
supplemental pilot channels, here, pursuant to operation of another
embodiment of the present invention.
[0034] FIG. 4 illustrates a representation of an exemplary power
control subchannel structure of the reverse pilot and supplemental
pilot channels defined pursuant to an embodiment of the present
invention.
[0035] FIG. 5 illustrates a representation, similar to those shown
in FIGS. 2-3, here showing the relationship between the data rates
at which data is communicated upon the reverse supplemental channel
and the power level of a pilot signal generated upon a reverse
pilot channel pursuant to operation of an embodiment of the present
invention.
[0036] FIG. 6 illustrates a timing diagram representing the timing
relationship of rate request and grant scheduling pursuant to
operation of an embodiment of the present invention.
[0037] FIG. 7 illustrates a representation of the generation of
rate indications on a reverse pilot channel generated pursuant to
operation of an embodiment of the present invention.
DETAILED OF THE DESCRIPTION
[0038] Referring first to FIG. 1, a radio communication system,
shown generally at 10, provides for radio communications, in a
multi-user environment, with mobile stations, of which the mobile
station 12 is representative. The communication system forms a
multiple data rate conmunication system in which data is
communicated, selectably at a selected data rate of a plurality of
separate, allowable data rates. In the exemplary implementation,
the communication system forms a CDMA 2000 cellular communication
system that provides for 1xEV-DV communication services. That is to
say, in the exemplary implementation, the communication system is
compliant, generally, with the operating protocols set forth in the
CDMA 2000/1xEV-DV operating specification.
[0039] The teachings of the present invention, are, however,
amenable for use in other types of multi rate data communication
systems. While the following description of operation of various
embodiments of the present invention shall be described with
respect to their implementation in a CDMA 2000 cellular
communication system that provides for 1xEV-DV data communications,
the teachings of the present invention are analogously applicable
to other types of communication systems.
[0040] Two-way communication of data between a mobile station and a
network part of the communication system is provided. A radio air
interface is defined between the network part of the communication
system and mobile stations operable therein. Forward link channels
are defined upon forward links extending from the network part to
the mobile stations. And, reverse link channels are defined upon
reverse links extending from the mobile stations to the network
part of the communication system. Both control information and data
traffic is communicated between the network part and the mobile
stations upon the forward and reverse link channels.
[0041] The operating specification pursuant to which the
communication system is constructed to be in compliance defines
various control and data channels upon the forward and reverse
links. Of significance to an embodiment of the present invention,
in the exemplary implementation, a reverse fundamental channel
(R-FCH) and a reverse supplemental channel (R-SCH) are defined upon
which to communicate, from a mobile station to the network part,
traffic data, communicated pursuant to effectuation of a data
communication service. The arrow 14 represents the reverse
fundamental channel upon which data is communicated by the mobile
station 12 to the network part of the communication system, and the
arrow 16 is representative of a reverse supplemental channel upon
which traffic data is also communicated by the mobile station to
the network part. More particularly, the reverse supplemental
channel is generally utilized upon which to communicate 1xEV-DV
data at any of various selected data rates. The data rates at which
the data is communicated upon the reverse supplemental channel is
susceptible to abrupt changes.
[0042] Various control channels are also defined on the reverse
link. Included amongst the control channels is a reverse pilot
channel (R-PICH), represented by the arrow 22. Pursuant to an
embodiment of the present invention, an additional channel, a
reverse supplemental pilot channel (R-SPICH) is defined. The
reverse supplemental pilot channel is represented in the Figure by
the arrow 22. And, forward link channels, both traffic and control
channels, are represented in the Figure by the arrow 28.
[0043] The network infrastructure of the communication system is
here shown to include a base station 34. The base station includes
transceiver circuitry for transceiving data upon the forward and
reverse link channels defined upon the radio air interface
extending between the network part and the mobile stations of the
communication system. In the exemplary implementation, the base
station operates pursuant to a CDMA (code-division,
multiple-access) communication scheme. The base station further
includes circuitry and elements to perform various functions, such
as power control functions that power control of signals generated
during operation of the communication system.
[0044] The base station 34 forms a portion of a radio access
network portion of the network part of the communication system.
The radio access network also includes a base station controller
(BSC) 36 to which the base station 34 is coupled. The base station
controller operates, amongst other things to control operation of
the base station 34, as well as other base stations to which the
base station controller is coupled. The radio access network is
here shown to be coupled to a packet data network (PDN) 38, here by
way of a gateway (GWY) 40. A correspondent node (CN) 42 is coupled
to the packet data network. The correspondent node is
representative of a communication node that forms an ultimate
source, or ultimate destination, of data communicated with the
mobile station 12. A computer station, a telephonic station, and a
content server are all exemplary of devices of which the
correspondent node can be comprised.
[0045] Various elements of the base station 34 are also represented
in FIG. 1. Here, the front end transmit and front end receive
circuit portions 48 and 52, respectively, are shown. The front end
transmit and receive portions perform functions such as
up-conversion and down-conversion, respectively, operations upon
data that is communicated upon the radio air interface. The front
end receive circuitry portion is coupled to a decoder and to a
signal-to-noise ratio (SNR) estimator 56. And, the decoder is
coupled to a frame error rate (FER) estimator 58. The estimators 56
and 58 operate upon indications of data received by the front end
receive circuitry to generate estimates of signal to noise ratios
and frame error rates of the indications provided thereto. Values
representative of the estimate generated by the estimator 56 on the
line 62 are provided to a comparator 66. And, values representative
of the estimates generated by the estimator 58 on the line 67 are
provided to an outer loop power control element 74. The elements 66
and 74 form portions of the transmit chain of the base station A
value of a target frame error rate (TG FER) 75 is also provided to
the outer loop power control element 74. The outer loop power
control element forms a value that is applied to the comparator 66,
and a comparator output is provided to the front transmit circuitry
48. Power control is effectuated through the communication of,
inter alia., power control commands that instruct the mobile
station as to at what power levels at which to communicate data on
the reverse data channel (R-FCH).
[0046] As mentioned previously, pilot signals are communicated by
the mobile station to facilitate coherent demodulation of the data
communicated upon the reverse data channels. The pilot signal is of
an adequate power level to permit the informational content of the
data communicated by the mobile station to the network
infrastructure adequately to be recovered. Because of the direct
relationship between the power level at which the pilot signal must
be sent and the data rate at which the traffic data is sent, and
its effect upon power control, conventionally the power level at
which the pilot signal is sent is set to be of a power level
corresponding to the power level required of the pilot signal
associated with data communicated at a highest possible data rate.
When data is communicated at a data rate less than the highest
possible data rate, the power level of the pilot signal is
unnecessary.
[0047] An embodiment of the present invention comprises apparatus,
shown generally at 82, embodied at mobile stations, such as the
mobile station 12. The apparatus includes a second pilot, or other
control, signal generator 84. The signal generator generates a
pilot signal of a power level responsive to the data rate at which
data is communicated by the mobile station upon the reverse
supplemental channel. In one implementation, the pilot signal is
unmodulated. In other implementations, the pilot signal is
modulated by a known sequence, by a pseudodeterminative sequence,
or by other values. The indication of the data rate at which the
data is communicated by the mobile station upon reverse
supplemental channel is provided to the second pilot signal
generator by way of the line 86. The indication is here represented
to be provided by a data source that forms part of the transmit
chain, together with the transmit circuitry of the mobile station.
And, the signal formed, or caused to be formed, by the second
control signal generator is communicated by the transmit circuitry
of the mobile station. As the data rate changes, the power level of
the additional pilot signal formed by the signal generator 84
correspondingly changes, thereby matching the power level of the
signal with the data rate of the traffic data that is
communicated.
[0048] FIG. 2 illustrates a representation of exemplary data rates
of data communicated upon the reverse fundamental channel 14 and
the reverse supplemental channel 16 during successive time frames
or other time periods. And, corresponding power levels at which
pilot signals are sent upon the reverse pilot channel 22 and
reverse supplemental pilot channel 24 pursuant to operation of an
embodiment of the present invention are also represented. In this
implementation, the power level of the pilot signal sent by the
mobile station upon the reverse pilot channel 24 is of a pilot
power level needed for operation of the reverse fundamental
channel. That is to say, the T/P ratio of the reverse fundamental
channel is independent of the rate of the reverse supplemental
channel. The additional pilot power that is needed for operation of
the reverse supplemental channel 16 is provided by the supplemental
pilot signal sent on the reverse supplemental pilot channel 24.
When detected at the base station, fast power control is performed
based upon pilot signals sent on the reverse pilot channel only, or
upon both the reverse pilot channel and the supplemental pilot
signal sent upon the reverse supplemental pilot channel.
[0049] In the even of variable rate operation, i.e., when the data
rate at which the data is communicated on the supplemental channel
changes, the pilot signal sent upon the reverse pilot channel is
transmitted at a lowest possible power level that can ensure the
performance of the communication of the data on the reverse
fundamental channel. The power level of the supplemental pilot
signal sent upon the reverse supplemental channel is set to be:
P=(10 .sup.pilot_reference_level*0.125/10-1.0)*R-PICH.
[0050] If the T/P ratio of the reverse supplemental channel is
defined to be the ratio of the power of the reverse supplemental
channel to the power of the combination of the reverse pilot
channel and the reverse supplemental pilot channel, then the T/P
ratio of the reverse supplemental channel is set to a value of a
nominal attribute gain of the rate that is currently used. Power is
not wasted. And, as the T/P ratio of the reverse fundamental
channel is independent of the rate of the reverse supplemental
channel, the power control loop is not disturbed by the data rate
change in the reverse supplemental channel.
[0051] FIG. 3 illustrates again the relationships between the data
rates of the data communicated upon the reverse fundamental and
supplemental channels 14 and 16 and the power levels of the pilot
signals upon reverse pilot channel and reverse supplemental pilot
channel 22 and 24 during successive time frames. In this
implementation, the power level of the pilot signal sent by the
mobile station sent on the reverse pilot channel is set by the
mobile station. And, hence, the T/P ratio of the reverse
fundamental channel, all according to the data rate of the data
communicated upon the reverse supplemental channel in a previous
frame. As the base station knows also the data rate of the data
communicated upon the reverse supplemental channel during the prior
time frame, the base station also knows of the current T/P ratio of
the data communicated upon the reverse fundamental channel and
adjusts the outer loop power control set point accordingly. If the
current reverse supplemental channel requires additional pilot
power than provided on the reverse pilot channel during the current
time frame, the reverse supplemental pilot channel is used to
communicate a supplemental pilot signal to provide the extra
power.
[0052] In this implementation, the power control loop is not
independent of the data rate change of the reverse supplemental
channel. But, the power control loop is relatively undisturbed by
the rate change in that the base station is aware of how to adjust
the outer loop power control set point at each frame boundary. In
this scheme, an improved SNR estimate is provided for use upon
inner loop power control as the pilot signal sent on the reverse
pilot channel is generally of a relatively high power. Hence, the
power control made possible in this implementation is fairly
accurate.
[0053] FIG. 4 illustrates a representation, shown generally at 102,
of exemplary power control subchannel structures of the reverse
pilot channel 22 and the reverse supplemental pilot channel 24. As
illustrated, the reverse pilot channel is formed of a first portion
104 of a length of 1152 chips and a 384 chip-length reverse power
control subchannel 106. Similarly, the reverse supplemental pilot
channel 24 is also formatted to include a first portion 108 of a
1152 chip length and a 384 chip length portion 112 forming the
reverse pilot control subchannel values. A code, for example,
W.sub.32.sup.64 can be assigned to the reverse supplemental pilot
channel. Backward compatibility is preserved through use of this
type of structure.
[0054] FIG. 5 illustrates a representation of the relationship
between the data rates at which communication data is communicated
upon the reverse fundamental and supplemental channels 14 and 16
and the power level of the pilot signal sent upon the reverse pilot
channel. In this implementation, the reference level of the pilot
signal is delayed following a data rate change of the communication
data, communicated upon the data channels. At time 106, the outer
loop power control set point is as indicated by the opposing
arrows. This is the power control set point prior to a rate change
of data communicated upon the reverse supplemental channel. At time
108, the data rate of the data communicated upon the reverse
supplemental channel increases. Time 110 defines the start of a
subsequent time frame. And, thereafter, during a subsequent time
frame, the pilot power and outer loop set point is adjusted. During
this subsequent time period, the quality of the reverse fundamental
channel and the reverse supplemental channel is maintained. At time
112, the data rate of the data communicated upon the reverse
supplemental channel again changes. And, subsequent to time 114,
the pilot power is again adjusted. And, as indicated at the time
116, the outer loop set point is again indicated by the opposing
arrows.
[0055] During the first frame following the data rate change at the
time 108, a sequence of procedures is performed at the mobile
station. The T/P ratio of the reverse fundamental channel is
maintained. And, the T/P ratio of the reverse supplemental channel
is adjusted according to the nominal attribute gain of the new data
rate plus the difference between the pilot reference level and the
new data rate and the old data rate. During this frame, the power
level of the reverse supplemental channel is set according to the
new rate, but the target received SNR of the reverse pilot channel
and reverse fundamental channel are maintained at the same level as
in the prior frame. And, at the base station, as the base station
is unaware of the rate change of the data communicated upon the
reverse supplemental channel, the base station power control
actions continue as is no rate change has oceurred.
[0056] During the second time frames, commencing at the time 110,
following the data rate change, the mobile station adjusts the
power level of the pilot signal by the difference between the pilot
reference level of the new data rate and the old data rate.
Additionally, the T/P ratio of the reverse supplemental channel is
adjusted according to the nominal attribute gain of the new data
rate. And, the T/P ratio of the reverse fundamental channel is
adjusted according to the multiple channel gain of the new data
rate. At the base station, the rate indicator in the first frame
following the data rate change is received. The base station
thereby has knowledge of the new data rate. And, the base station
adjusts the outer loop power control threshold to the initial
target outer loop power control threshold of the new data rate.
[0057] FIG. 6 illustrates rate requests 118, rate grants 122, and
reverse supplemental channel values 124 during operation of an
embodiment of the present invention. In this implementation, data
rate changes and power level adjustments, and adjustments to the
T/P ratios are made according to the nominal attribute gain and
multiple channel adjustment gains, all as specified in the
operating specification of CDMA 2000. Without the knowledge of the
current rate, the base station assumes the mobile station to
transmit at a highest rate allowed by the previous rate grant. And,
the outer loop power control threshold is set accordingly.
[0058] In the exemplary operations set forth in FIG. 6, the rate of
the data communicated upon the reverse supplemental channel is
always equal to or less than, the data rate that is granted by the
base station. That is to say, Rate_I is less than or equal to
Rate_grant_I. Because the base station does not know the data rate
of the data communicated upon the reverse supplemental channel
until the rate indicator is received correctly, the base station
assumes the current rate, Rate_I equals the Rate_grant_I. And, the
outer loop power control threshold is set accordingly. Through this
operation, there is always enough power in the pilot signal sent on
the reverse pilot channel to guarantee the required frame error
rate on the reverse supplemental channel.
[0059] FIG. 7 illustrates an implementation in which a fast rate
indication is multiplexed into the reverse pilot channel, thereby
to provide the base station with an indication of the data rate
change at the earliest possible time. The first sequence 126,
illustrates the reverse pilot channel and the reverse power control
subchannel during successive time periods within a time frame, each
defining a power control group 128.
[0060] The second sequence illustrates the reverse pilot and
reverse pilot channel and reverse power control subchannel together
with a reverse fast rate indication subchannel (R-FRISCH) 132
defined pursuant to an embodiment of the present invention. And,
the third sequence illustrates the reverse pilot channel, the
reverse fast rate indication subchannel and reverse power control
subchannel defined pursuant to operation of another embodiment of
the present invention.
[0061] As the Figure illustrates, selected power control bits, such
as the first one or two power control bits of the reverse link
power control subchannel are punctured with values that define the
reverse fast rate indication subchannel. In one implementation, a
pilot signal generator, such as the pilot signal generator 84 shown
in FIG. 1 also operates as a rate indication generator that
generates rate indications that indicate the data rate that is
inserted into the illustrated positions. In another implementation,
the values are inserted even earlier. Alternately, the mobile
station can also puncture a portion of the reverse pilot channel in
the first and second power control group. The rate indication bits
inserted into these positions form this subchannel, the R-FRISCH.
The mobile station changes data rates and adjusts the power levels
and T/P ratios according to the nominal attribute gain and multiple
channel adjustment gain, all as specified in the operating
specification of the CDMA 2000 system. The base station holds the
outer loop power control thresholds in the first one or two power
control groups of this frame, and adjusts the outer loop power
control threshold thereafter according to the rate change
information conveyed in the reverse fast rate indication
subchannel. Fast rate indication can alternately be realized in
other manners, such as by multiplexing the values together with the
reverse rate indicator channel (R-RICH). The definition and use of
the R-FRISCH permits a base station to adjust the outer loop power
control threshold quickly. The bits can also be used together with
the R-RICH to decode the detail rate indication information in a
finer resolution.
[0062] Through operation of any of these embodiments of the present
invention, 0 fast stabling of the power control loop is provided
with minimal change to the existing operating specification.
[0063] The preferred descriptions are of preferred examples for
implementing the invention, and the scope of the invention should
not necessarily be limited by this description. The scope of the
present invention is defined by the following claims.
* * * * *